Commercial soft drinks typically contain from 3.5 to 4 volumes of carbon dioxide at approximately 60 degrees Fahrenheit. For two liters of soda this comes to 14 to 16 grams of carbon dioxide. Seltzer may contain up to 5 volumes of gas. In one volume of water, one volume of carbon dioxide is soluble at 60 degrees Fahrenheit at one atmospheric pressure. Increasing amounts of carbon dioxide can be dissolved as temperature decreases and/or as pressure increases. For example, at 32 degrees Fahrenheit and 20 pounds per square inch gauge (psig), 4 volumes of carbon dioxide can be added to one volume of water.
Fermentation of carbohydrates is a natural process. Yeast and water are added to a fermentable carbohydrate. The resulting mixture is changed by the biological action of the yeast on the carbohydrate, forming alcohols and carbon dioxide as the primary byproducts. Grapes on vines may often have yeast that collects on the grape skin; when the grape is crushed to make grape juice, the yeast can react with the sugars in grape juice to form wine and carbon dioxide.
In the past, soft drinks were made by adding yeast to flavored sugar water, sealing the solution in a glass bottle, and leaving it to ferment. This technique resulted in the potential for dangerously high pressures, sometimes causing the bottle to explode. In addition, the fermentation byproducts and the yeast flavor resulted in an off taste.
Modern carbonation devices work well for large-scale production. There has not been a low-cost, easy-to-carbonate method using natural yeast fermentation, suitable for home use that utilizes disposable bottles as the carbon dioxide generating container which also holds the generated carbon dioxide in disposable reservoir bottle(s), and which uses reservoir bottles containing pressurized carbon dioxide for carbonating into a disposable receiver bottle.
U.S. Pat. No. 4,923,969 discloses a carbonation cap that has an integral check valve without a barbed fitting connection. It has no provision for a tube to be mounted inside the container for siphoning. U.S. Pat. No. 4,940,212 discloses a custom bottle and cap assembly with an integral spring-loaded check valve in the cap being charged by a conventional high pressure carbon dioxide tank. U.S. Pat. No. 5,366,745 discloses a chemical carbon dioxide generator but does not specify how pressure is maintained in the single disposable receiver bottle that takes 12 hours for some level of carbonation to occur. U.S. Pat. No. 7,296,508 discloses a reactor bottle consisting of a test tube containing a reactive chemical connected to a receiver bottle. The test tube must be tilted in order for its contents to mix with the contents of the bottle after the flanged connections to the cap are sealed. U.S. Pat. No. 5,396,934 teaches the unnecessary step of removing air from the receiver bottle, before adding carbon dioxide from a high pressure tank, which requires a step down pressure regulator. U.S. Pat. No. 5,505,345 is a carbonation dispensing cap with an integral valve which has no provision for adding carbon dioxide to a soda bottle. U.S. Pat. No. 4,423,670 discloses a single apparatus in which the alcohol is not separated from the receiver mixture and in which there is no pressure relief valve to set an exact carbonation level.
The prior art for home generated carbon dioxide does not store carbon dioxide whether by fermentation or by chemical means, nor does it have the separation of the reactor bottle yeast, alcohols, and water in a separate two volumes or more reservoir before adding it quickly to a ready single volume receiver bottle.